Use of a nonionic surfactant to improve nitrogen use efficiency of potato

Overhead sprinkler irrigation of potato (Solanum tuberosum L.) grown on sandy soils has sometimes resulted in nonuniform wetting of potato hills and the creation of a dry zone within the potato hills. This study conducted in 2000 and 2001 evaluated the use of a nonionic surfactant, sprayed in the seed piece furrow at planting, to improve nitrogen use efficiency of Russet Burbank potato. The experimental design was a two variable complete factorial, in randomized complete blocks with four replications, with surfactant (+ or - at 9.3 L/ha) as the first variable and N rate (0, 134, 202, or 269 kg N/ha) as the second. In addition to measuring tuber yield and grade, crop N status was monitored by petiole nitrate-N levels several times during the growing season as was tuber N uptake and soil water NO3-N concentrations below the root zone. Yield results showed a tendency for a significant interaction between surfactant use and N rate with optimum N rate about 60 kg/ha lower where the surfactant was used in 2000, but in 2001 this trend was not apparent. In both years, a clear trend (p=0.07 to 0.16) existed toward an increase in yield of US#1, 170 to 370 g tubers with surfactant use. Tuber N uptake was significantly increased by surfactant in 2001. Plant and soil N parameters also showed some responses to the surfactant applications. These preliminary data show that some improvements in N use efficiency may be realized by using a surfactant to keep a greater proportion of the hill moist and contributing to N uptake.